Band-gap voltage reference circuits are routinely used in integrated circuit applications that require a reference voltage that is reasonably precise and stable over a range of temperatures. Fundamentally, a band-gap voltage reference circuit includes two bipolar base-emitter junctions operating at different current densities. The reference voltage is obtained by summing one of the base-emitter voltages with a scaled difference of the two base-emitter voltages. Since the base-emitter voltage is inversely proportional to temperature and the scaled difference voltage is directly proportional to temperature, their sum is temperature independent to the first order. However, the reference voltage still exhibits some second and higher order nonlinearity (curvature) with temperature, and various techniques have been developed to compensate for these nonlinearities. For example, the circuitry of the reference generator can be trimmed or calibrated at a number of different temperature settings, and/or various non-linear waveforms can be used to cancel out the non-linearity of the reference. Also, special steps must be taken to minimize stresses caused by the circuit packaging because package stress non-uniformity can introduce additional voltage instability over time.
Conventional approaches for addressing the curvature compensation and package stress issues typically result in a component cost that is too high for many applications. Accordingly, what is needed is a high-precision curvature-compensated band-gap voltage reference circuit that is low in cost, easily calibrated, and substantially insensitive to packaging stresses.